The battery industry currently lacks techniques which have attributes of being scalable, consistent, non-destructive, stand-alone, etc., for detecting physical characteristics and changes thereof in a battery during manufacturing or in use. Some conventional techniques for battery diagnostics involve measuring physical characteristics of batteries such as temperature, internal pressure, stress-strain, open circuit voltage, direct current (DC) impedance, alternating current (AC) impedance, and current-voltage characteristics.
Information gathered about a battery using the above techniques can be used to infer different aspects of the overall condition of the battery. For example, an increase in temperature in a Lithium-ion (Li-ion) battery during charge-discharge cycling of the Li-ion battery can indicate the charge-discharge rate or power output of the Li-ion battery. Alternatively, the increase in temperature can indicate potential formation of internal short circuits or breakdown of electrolytes in the Li-ion battery. In another example, a strain gauge placed at a surface of a pouch cell type battery can be used to detect a buildup of pressure within the pouch cell (e.g., due to formation of gas within the pouch cell); or to detect a degradation state of electrodes within the pouch cell.
Electrochemical-acoustic signal interrogation (EASI) is another diagnostic technique that uses ultrasound signals to measure changes in the physical properties of batteries. EASI operates on the principle that the acoustic behavior of a battery is sensitive to any change in physical properties along a path traveled by sound waves of the ultrasound signals. Accordingly, EASI may be used to directly and actively probe internal components of the battery (wherein, it will be recognized that electrical, thermal, and strain-based diagnostic techniques are not capable of such probing as is made possible by EASI). In addition, EASI is also agnostic to chemistries or geometries of batteries. EASI may also be implemented with minimal hardware, such as a pair of transducers in direct contact with the body of the battery.
With reference to FIG. 1, a schematic of system 100 comprising example hardware for EASI is shown. System 100 comprises battery 102, to which a pair of transducers 108a-b may be affixed on two locations (e.g., on opposite sides) on the surface of battery 102. Hardware such as screws 106a-b are shown, but other alternative means for affixing transducers 108a-b to the body of battery 102 may be used. Battery cycler 110 represents a controller for charging-discharging battery 102 and may be connected to battery 102 through terminals 104a-b of battery 102. Ultrasonic pulser/receiver 112 is coupled to transducers 108a-b, wherein through the control of one of ultrasonic pulser/receiver 112, one of transducers 108a-b is configured to transmit ultrasonic signals while the other one of transducers 108a-b is configured to receive the transmitted ultrasonic signals. A computer (not separately shown) which may be provided within or coupled to the block identified as ultrasonic pulser/receiver 112 may be configured to analyze the received ultrasonic signals and infer the characteristics of battery 102 according to EASI techniques.
Although a wide variety of physical sensors may be employed by a EASI system such as system 100, it is observed that a single sensor type may not be able to detect all aspects of the physical characteristics and changes thereof that may determine a battery's condition. Hence, some battery diagnostic approaches may employ two or more measurement techniques using different sensor types to obtain a more complete picture of the condition of the batteries, especially while the batteries are in use. However, with the exception of electrical testing methods, in which the electrical leads are connected to the tabs of the batteries there is no standard method in the art for maintaining physical contact between the measurement sensors, particularly EASI sensors such as transducers 108a-b and the surface of the battery's body.
There is accordingly a need for modular, adaptable holders that can be used for different types of batteries (e.g., cylindrical batteries, pouch type cells, etc.) which are compatible with and can accommodate multiple types of measurement sensors.